The objective of this project is to determine the functional relationships between individual central nervous system (CNS) vasomotor control systems (commonly called vasomotor "centers" or "pathways"). The cardiovascular effects of vasomotor interactions will be studied within individual organs or tissues. In addition, their effects on the redistribution of cardiac output and on arterial and venous blood pressures will be analyzed. The study of interactions between vasomotor systems will provide two types of information. The first type will consist of descriptions of the cardiovascular effects of separate and simultaneous electrical stimulation of individual central vasomotor systems. Cardiovascular output will be assessed by measuring arterial and venous pressures, regional blood flows to skeletal muscle, mesenteric and renal vascular beds and cardiac output. These descriptions will provide immediate insight into the types of vasomotor interactions which occur, their relative importance in various vascular beds and their roles in redistributing cardiac output and modifying blood pressure. The second type of information will consist of the loci of vasomotor interactions. This information will be obtained by combining the techniques of simultaneous stimulation with focal lesions, careful neuroanatomical mapping and pharmacological stimulation and blockade.